Low profile fusion cage and insertion set

ABSTRACT

A bone fusion implant system including a first implant body having substantially flat top and bottom surfaces for engaging opposing vertebrae and a side wall extending between the top and bottom surfaces, the side wall including a concave recess and a second implant body having substantially flat top and bottom surfaces for engaging the opposing vertebrae and a side wall extending between the top and bottom surfaces thereof, the side wall of the second implant including an arcuate portion adapted to be received within the concave recess for enabling the first and second implant bodies to be positioned in nested side-by-side relation between the opposing vertebrae.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a divisional of U.S. patentapplication Ser. No. 09/545,320, filed Apr. 7, 2000, which claimsbenefit of U.S. Provisional Application No. 60/128,113, filed Apr. 7,1999. The disclosures of the '320 and '113 applications are herebyincorporated by reference herein.

BACKGROUND OF THE INVENTION

[0002] The present application relates to a low profile fusion cage andan insertion set for the low profile fusion cage.

[0003] Known spinal implants, such as those used for vertebral fusion,are often used in pairs to provide adequate, evenly distributed supportand fusion inducement. Because of limited space for implantation and forsurgical maneuvering, it is sometimes difficult or unfeasible toimplement a pair of implants that otherwise have desirable dimensionsand attributes. Certain existing implant designs are configured forclose, adjacent placement to other implants, but none achieve optimumperformance, versatility or ease of insertion.

SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide an implantdesign, and associated instruments and methods, that provide optimumconfigurations for placement of adjacent implants in close proximitywith optimum performance. These objects and others are achieved throughthe present invention implant configuration and associated instrumentsand method.

[0005] In a preferred embodiment, a fusion implant according to thepresent invention is provided with a concave cut-away portion on acircumferential surface of an elongated implant. The concave portionaccommodates the outer contour of an adjacently placed implant having acorresponding concave surface. A novel dual tang distractor tool isprovided with two over-lapping cross-sectional configurations tofacilitate close insertion and placement of implants according to thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Preferred embodiments of the present disclosure are describedherein with reference to the drawings wherein:

[0007]FIG. 1 is a perspective view of the fusion cage of the presentdisclosure;

[0008]FIG. 2 is a side view of the fusion cage of FIG. 1;

[0009]FIG. 3a is a cross-sectional view of the fusion cage taken alonglines BB of FIG. 1;

[0010]FIG. 3b is a cross-sectional view of the fusion cage as shown inFIG. 3a, with a conventional implant cage of similar view placedadjacently thereto.

[0011]FIG. 4 is a perspective view of the tang retractor of the presentdisclosure;

[0012]FIG. 5 is a perspective view of the guide of the presentdisclosure;

[0013]FIG. 6 is a perspective view illustrating attachment of the guideto the tang retractor,

[0014]FIG. 7 is a perspective view of the plate of the impactor;

[0015]FIG. 8 is a front, perspective view of an alternative embodimentof the present invention; and

[0016]FIG. 9 is a front, perspective view of another alternativeembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017] FIGS. 1-3 a illustrate perspective, side and end views of the lowprofile fusion cage (10) of the present invention. The present inventioncage (10) is of the type known commercially as the Ray TFC™ Fusion Cagecurrently marketed by Surgical Dynamics, Inc. The Ray TFC™ Fusion Cageis disclosed in commonly assigned U.S. Pat. No. 4,961,740, the contentsof which are incorporated herein by reference.

[0018] The fusion cage (10) disclosed herein can be implemented withanother fusion cage to reduce the total amount of space occupied by twoconventional fusion cages placed side by side. The fusion cage (10) hasa helical thread (14) for facilitating insertion and securing of thecage (10) in a vertebral disc space. The thread (14) is carved out toform concave portions (16, 17) to reduce the profile of the thread. Asshown, the concave portions (16, 17) are preferably provided 180 degreesapart. If desired, only one concave portion is necessary to carry outthe present invention. It is possible, also, to provide more than twoconcave portions if desired. The concave portions (16, 17) allow two ormore cages (10, 11) to be placed close together as the radiused portionof one cage (11) is placed within the concave portion (17) of anadjacent cage (10), as shown in FIG. 3b. As can be appreciated, thecombined width (transverse space) of the two low profile cages (10, 11)placed in this fashion is less than the combined width if twoconventional cages without at least one of them having a concave portionwere placed side by side.

[0019] FIGS. 4-7 b illustrate an insertion instrument set for fusioncages according to the present invention. The instrument set includes atang retractor (20), a guide (30) and an impactor (40) and impactorplate (41). The tang retractor (20) includes a pair of spaced aparttangs (21) which are dimensioned and configured as wedges at the distalend for insertion into and distraction of the disc space. Theconfiguration of the tangs (21) and the manner in which they distractthe disc space is described in pending U.S. patent application Ser. No.08/889,661, filed Jul. 8, 1997, the contents of which are incorporatedherein by reference.

[0020] The tang retractor (20) includes a pair of proximally extendingslotted tabs (22) for mounting the tabs (42) of the impactor plate (41)when the impactor plate (41) is mounted to the proximal end of thedistractor (20). The tabs (42) are inserted into the slots (23) of thetabs (22) to mount the impactor plate (41) and the elongated integralimpactor (40), which is connected to the impactor plate (41) by threads(43, 45), to the tang retractor (20). The impactor (40) can then beimpacted or tapped at its proximal end (47) by a suitable tool, such asa hammer, to insert the tang (21) into a vertebral space. Afterinsertion, the tabs (42) are slid out of engagement with slots (23) toseparate and remove the impactor (40) and impactor plate (41), leavingthe tang retractor (20) in place with the tangs (21) inserted in thevertebral space.

[0021] The guide (30) is then attached to tang retractor (20) byinserting the distal end pin (32) into the longitudinal slot (25) of theretractor (20). The distal end pin (32) is seated within the slot (25)50 that the guide (30) can be pivoted, about the pin (32), with respectto the fixed tang retractor (20) between alignment with each of the twoopenings (26, 27) of the tang retractor (20), respectively. Each of theopenings (26, 27) is configured to receive a fusion cage along with aconventional cage insertion tool (not shown). The guide (30) is rotatedabout pin (32) 50 that its axial bore (34) is aligned with one of theopenings (26, 27) of the tang retractor (20) during hole preparationthrough a respective one of the openings. Suitable tools, such as thosedescribed in the aforementioned application Ser. No. 08/889,661, areinserted through the bore (34) to prepare the space for fusion cageinsertion. Fusion cages such as the type of the present invention, arethen inserted via an elongated insertion tool through the bore (34) andthe respective tang retractor opening (26, 27) for placement within thevertebral space. Each cage is placed so that one of the concave portions(16, 17) faces the adjacent opening or bore in the vertebral space. Theguide (30) is subsequently rotated so that axial bore (34) is alignedwith the other opening (26, 27) in the retractor 20. Another fusioncage, either with or without concave portions, is inserted in a similarmanner as described above so that its outer circumferential portion fitswithin the concave portion (16, 17) of the first-inserted fusion cage.

[0022] It is contemplated that an interlocking device (33) be providedto retain the guide (30) in each of its two aligned positions relativeto the tang retractor (20) during site preparation and insertion of afusion cage therethrough.

[0023] Alternate embodiments of the present invention, such as thoseshown in FIGS. 8-9, include variously configured implant bodies having-aconcave portion to facilitate close, adjacent placement with additionalimplant bodies. For instance, the implant body (100) in FIG. 8 is ahalf-oval having a central opening (102) to facilitate bone fusion, anda concave side wall (104) configured to matingly receive acircumferential, convex wall (106) of an adjacent, oval implant (108).The implant body (200) of FIG. 9, is generally cylindrical and has aconcave channel (202) aligned generally perpendicularly to alongitudinal axis running between open ends (204, 206).

[0024] It can be appreciated that the tang retractor (20) having alength approximately equal to its width increases visibility as well asenables the user to more easily remove extraneous disc tissue because ofthe increased mobility of instruments, e.g. rongeurs, inserted throughthe retractor 20. While this is the preferred embodiment, the length ofthe retractor (20) may be varied as desired to achieve differentadvantages.

[0025] While the preferred embodiment has been disclosed herein, it isunderstood and contemplated that modifications and variations may beemployed without departing from the scope of the present invention.

1. A bone fusion implant system comprising: a first implant body havingsubstantially flat top and bottom surfaces for engaging opposingvertebrae and a side wall extending between said top and bottomsurfaces, said side wall including a concave recess; a second implantbody having substantially flat top and bottom surfaces for engaging theopposing vertebrae and a side wall extending between said top and bottomsurfaces thereof, said side wall of said second implant including anarcuate portion adapted to be received within said concave recess forenabling said first and second implant bodies to be positioned in nestedside-by-side relation between said opposing vertebrae.
 2. The system asclaimed in claim 1, wherein said first implant body defines an internalcavity adapted to receive bone growth inducing substances.
 3. The systemas claimed in claim 2, wherein at least one of the top and bottom facesof said first implant body is in communication with the internal cavityof said first implant body.
 4. The system as claimed in claim 1, whereinsaid second implant body defines an internal cavity adapted to receivebone growth inducing substances.
 5. The system as claimed in claim 4,wherein at least one of the top and bottom faces of said second implantbody is in communication with the internal cavity of said second implantbody.
 6. The system as claimed in claim 1, wherein said first and secondimplant bodies are made of bone.